IPB Explains the 'Bediding' Phenomenon Causing Colder Air During the Dry Season
Dr Givo Alsepan, a lecturer in the Department of Geophysics and Meteorology at the Faculty of Mathematics and Natural Sciences (FMIPA) at IPB University, has explained that the colder air felt at night and in the morning during the dry season is a natural phenomenon known as bediding. In a statement issued in Bogor on Wednesday (22/7/2026), Givo said the bediding phenomenon is not a direct impact of climate change, but rather part of seasonal climate dynamics that commonly occur between June and September.
“Bediding is an atmospheric phenomenon that occurs normally during the dry season. It is a manifestation of physical atmospheric processes. The condition arises when the daily minimum temperature drops quite significantly as a result of highly effective radiative cooling,” he said.
He explained that bediding is triggered by a combination of atmospheric conditions common in the dry season. One of the main causes is the tendency for clear skies at night, which allows heat absorbed by the Earth’s surface during the day to be released back into the atmosphere and outer space more easily.
In addition, the air during the dry season is generally drier than during the rainy season. The reduced water vapour content in the atmosphere means less heat is retained, making the cooling process more effective.
“When the air is drier, the release of heat from the Earth’s surface takes place more effectively. As a result, the air at night through to the morning feels far colder,” he said.
According to Givo, the phenomenon is more pronounced in mountainous and highland areas because of the higher elevation and the tendency for cold air to pool in valleys. In areas such as the Dieng Plateau, the condition can even trigger the formation of frost or dew known as embun upas.
He added that the Australian monsoon winds also reinforce the bediding phenomenon. During the dry season, Australia is experiencing winter, so the air masses moving towards Indonesia carry cooler and drier air, particularly to regions south of the equator such as Java, Bali and Nusa Tenggara.